(1) Field of the Invention
This invention relates to elastomeric impulse energy storage and transfer systems, and is directed more particularly to an elastomeric pump of the type used to eject devices from an underwater vehicle into a surrounding fluid medium.
(2) Description of the Prior Art
Impulse energy storage and transfer systems are known and are used to eject devices, such as torpedoes, from underwater vehicles, such as submarines. In U.S. Pat. No. 4,848,210, issued Jul. 18, 1989 to Laurent C. Bissonnette, there is shown and described an impulse energy storage and transfer system having as a principal component thereof an elastomeric energy storage device. The elastomeric device is adapted to accept and store a working fluid. In accepting the working fluid, the elastomeric means, a bladder-type accumulator, becomes distended. Upon opening of the accumulator for egress of the working fluid, the stored energy is rapidly converted into kinetic energy for quietly ejecting a projectile or other body, along with the stored fluid, from the system and into a surrounding medium, typically seawater. In U.S. Pat. No. 5,200,572, issued Apr. 6, 1993 to Laurent C. Bissonnette, there is shown and described an improved embodiment of elastomeric accumulator.
The U.S. Navy launches devices from submarines using hydraulic impulse pumps of the type shown and described in the Bissonnette patents to obtain the required launch impulse. In most of the systems used, provisions are made to launch devices at a selected one of two exit velocities. Accordingly, two launch pump energy levels are required. The use of a single elastomeric member as a launch pump requires that the two velocities be achieved by incurring different levels of friction loss between the pump and the launch tube. Such is obtained by choking the flow to achieve the lower of the two exit velocities. However, choking has been found to be undesirable because of the complexity of the choking valve system, the loss of efficiency in use of a high-velocity firing for a low-velocity launch, and cavitation problems. An alternative solution is to provide two separate pumps, but such arrangements require two launch valves and two impulse tanks, with consequent cost escalations.
There is thus a need for an impulse pump having the capability of effecting launches at two or more exit velocities, without flow choking means and without additional launch valves and impulse tanks.